Insert Plates and WRC-107

[Ebardt]

When modeling an insert plate at a Nozzle you can generally determine the required size of the insert plate for nozzle reinforcement by setting the "User Specified Limit of Reinforcement" in the Nozzle dialog/area screen.

However, it appears that when you add external nozzle loads and run WRC-107 or FEA calculations Compress does not take into account the "User Specified Limit of Reinforcements". The WRC-107 results are analyzed using the "Local Shell Thickness" given for the insert plate regardless of the diameter of this insert plate. The FEA results assume the entire vessel is the thickness of the insert plate and no discontinuity is shown at the insert plate and vessel shell seam.

WRC-107 Appendix A-5 limits taking credit for the thickness of the insert plate unless the width of the insert plate is equal to or greater than 1.65*(RT)^.5. Compress does not appear to take this limit into account.

I fear that this approach leads many designers into a false assurance that their nozzle is designed sufficiently when, in fact, it may not be.

Tom, I would appreciate your comments on this matter. Or if anyone else has come across this situation and has any input, please reply.

 

[TomBarsh]

The "local thickness" option was intended for purposes of modeling a local thickness around the nozzle that was subjected to a different local corrosion or erosion; it was not planned for purposes of modeling an insert plate.

The local thickness option can be used to model an insert plate for purposes of area replacment, etc. However, as you describe there are considerations in WRC-107 that may not be treated in this approach.

Some time back I added a request to our program development list for a more complete treatment of insert plates. Unfortunately, this is not high on the priority list.

Tom Barsh
Codeware Technical Support